Conventionally, in the system for processing a plate material, a nominal value of a work, for example a material of SPCC, and a plate thickness of 1.6, is entered to an automatic programming machine. Based on this nominal value, an elongation value necessary for bending is calculated, and a developed dimension of a blank is calculated from this elongation value.
In blanking work before bending, punching of the blanks is carried out by a punching machine based on the developed dimension. Each blank is bent by a bending machine.
In the conventional system for processing a plate material, if a characteristic of a work to be actually processed is far from a nominal value, for example if an actual plate thickness is 1.5 mm while a nominal plate thickness is 1.6 mm, a correct developed length of the blank cannot be obtained at the automatic programming machine based on an elongation value generated by such a difference in plate thickness. Consequently, a problem has been inherent, i.e., an actual bent dimension after bending is not within an allowable range.
At some bending machines, a plate thickness of the work is measured by a plate thickness detecting function during bending of the work, and this measured plate thickness is applied to determination of a D value (stroke amount of a ram) for setting a bending angel. However, plate thickness information actually measured was simply used at a single bending machine. For example, a problem has been inherent, i.e., even if a plate thickness of the blank is measured by the plate thickness detecting function during bending, the developed dimension of the blank that has been punched cannot be corrected. Alternatively, a problem has occurred, i.e., correction of the blank necessitates time and labor of reprocessing.
The work has a plate thickness changed from place to place even on a sheet. Consequently, since a difference is generated in plate thickness of each blank, as described above, a problem has been inherent, i.e., a bent dimension is not within an allowable range.
Regarding the bending angle, it is known that the bending angle closer to an actual angle is obtained by calculating a spring-back amount or a stroke amount based on the actual plate thickness and the actual material constant rather than a nominal plate thickness and a nominal material constant (tensile strength, Young's modulus, an n value, an f value, or the like). However, unless the actual plate thickness or the actual material constant of the work is known before bending, it cannot be reflected on the developed dimension. Even if the material constant can be calculated from load/stroke information during first bending, this information is reflected from next bending.
The present invention was made to solve the foregoing problems. Objects of the invention are to provide a method for calculating material attributes, and a method and a system for processing a plate material, which enable bending work to be carried out efficiently and accurately by measuring the actual plate thickness and the actual material constant during punching before bending, and reflecting the measured information in the bending.